Fasting before certain blood tests is important to help make sure that your test results are accurate. Some tests are not impacted by food or drink and these can be taken without fasting. However, some tests require you to fast before collecting your sample, this is because various biomarkers can be affected by the intake of food and drink.
How will I know if the test I'm taking requires me to fast?
If you need to fast before taking your test, you'll be advised of this:
- At the time of purchase - On the product page for the test.
- When your purchase is confirmed - In the email you'll receive after you purchase the test.
- When you're ready to take/register the test - During the online registration process.
What are the rules of fasting?
- Stay hydrated by drinking clear water only.
- Take your sample in the morning.
- Eat anything for 8 hours before collecting your sample.
- Drink anything other than clear water for 8 hours before collecting your sample.
- Make any changes to your normal medication regime without talking to the prescriber.
What happens if I don't fast before collecting my sample?
If you don’t fast before taking a test that requires it, the reference ranges provided may not be relevant to your test results - as reference ranges provided by the laboratory for these biomarkers are based on what you would normally see after fasting.
If you forget to fast and you’ve eaten or drank something, please wait until the next day to take your test. Blood samples are best collected in the morning and this will also ensure that you’ve fasted for the necessary 8 hours.